Astronomy Beat is a twice-monthly, on-line column written by "insiders" from the worlds of astronomy research and outreach available exclusively to members of the Astronomical Society of the Pacific. As a public service, the nonprofit Society is making the issue on the origin of the Drake equation freely available to everyone. ... by Frank Drake and Dava Sobel . Click on the link above to view the pdf, or right-click (PC)/control-click (Mac) the link to download the file to your computer. ...